They give you 15GB of free space - 20GB if you sign up via this link: https://copy.com?r=9IfWjn - with a further 2GB for linking to your twitter account.

Basically you start with 22GB and have the ability to earn a further 5GB of free space per referral.

The interface is clean, the program works wonderfully, very fast, supports Wifi Sync and AES256 encryption, and they seem to have a client for just about everything (Mac, Windows, Linux, iOS and Android). It's exactly what Dropbox should have been.